How to fix NullReferenceException: Object reference not set to an instance of an object error,

Questions & Answers
1

I am working on an inventory and every time I opne it I get this error: NullReferenceException: Object reference not set to an instance of an object
Inventory.LoadUnloadInventoryMenu () (at Assets/Scripts/Inventory.cs:116)
Inventory.Update () (at Assets/Scripts/Inventory.cs:59)

This is the inventory.cs script:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class Inventory : MonoBehaviour
{
	//Keys used to open doors
	public bool hasRedKey, hasGreenKey, hasBlueKey;

	//the item the player is using
	public Sprite mainItem;

	public Sprite[] hotbar = new Sprite[3];


	//every item in the game
	public Sprite[] items = new Sprite[30];


	//items in the players inventory
	public Sprite[] inventory = new Sprite[20];

	//armor slots in thye players Inventory
	public Sprite[] armor = new Sprite[4];

	//the inventory menu
	public GameObject menu;

	void Start()
	{
		//Deactivating the menu
		menu.SetActive(false);

		//assinging values
		mainItem = items[0];
		FindObjectOfType<CanvasManager>().UpdateMainItem(mainItem);
		hotbar[0] = items[3];
		hotbar[1] = items[20];
		hotbar[2] = items[4];
		FindObjectOfType<CanvasManager>().UpdateHotbar(hotbar);

		for(int i = 0; i < 20; i++)
		{
			inventory _= items*;*_

* }*

* for (int i = 0; i < 4; i++)*
* {*
armor = items*;*
* }*
* }*

* void Update()*
* {*
* //checking if the player opened/ closed the inventory*
* if (Input.GetKeyDown(KeyCode.E))*
* {*
* LoadUnloadInventoryMenu();*
* }*

* //cycle through hotbar*
* if (Input.mouseScrollDelta.y == 1)*
* {*
* nextItem();*
* }*

* if (Input.mouseScrollDelta.y == -1)*
* {*
* prevItem();*
* }*
* }*

* private void nextItem()*
* {*
* Sprite temp = hotbar[0];*
* hotbar[0] = hotbar[1];*
* hotbar[1] = hotbar[2];*
* hotbar[2] = mainItem;*
* mainItem = temp;*
* FindObjectOfType().UpdateHotbar(hotbar);*
* FindObjectOfType().UpdateMainItem(mainItem);*

* }*

* private void prevItem()*
* {*
* Sprite temp = mainItem;*
* mainItem = hotbar[2];*
* hotbar[2] = hotbar[1];*
* hotbar[1] = hotbar[0];*
* hotbar[0] = temp;*
* FindObjectOfType().UpdateHotbar(hotbar);*
* FindObjectOfType().UpdateMainItem(mainItem);*
* }*

* private void LoadUnloadInventoryMenu()*
* {*
* if (menu.activeSelf)*
* {*
* //diactivatting the inventory when its open*
* menu.SetActive(false);*
* }*
* else*
* {*
* //activatting the inventory*
* menu.SetActive(true);*

* //null check*
* if(inventory != null && armor != null && hotbar != null)*
* {*

* //update the items to the correct value*
* GameObject.Find(“InventoryManager”).GetComponent().UpdateInventory();*
* GameObject.Find(“InventoryManager”).GetComponent().UpdateHotbar();*
* GameObject.Find(“InventoryManager”).GetComponent().UpdateArmor();*

* }*

* }*

* }*
}
The Canvas manager is used to display the UI visible throughout the game that displays things like health to the player. The “menu” object I assigned manually in the Unity Inspector as the InventoryManager object which is the InventoryUI.
This is the InventoryManager.cs file:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class InventoryManager : MonoBehaviour
{
* //definning inventory slots*
* public Image[] inventory = new Image[20];*
* public Image[] armor = new Image[4];*
* public Image[] hotbar = new Image[3];*

* //setting the hotbar slots to the correct values*
* public void UpdateHotbar()*
* {*
* Sprite[] toLoad = GameObject.Find(“Inventory”).GetComponent().hotbar;*

* for(int i = 0; i < hotbar.Length; i++)*
{
hotbar_.sprite = toLoad*;
}
}*_

* //setting the armor slots to the correct values*
* public void UpdateArmor()*
* {*
* Sprite[] toLoad = GameObject.Find(“Inventory”).GetComponent().armor;*

* for(int i = 0;i < armor.Length; i++)*
{
_ armor*.sprite = toLoad[0];
}
}*_

* //setting the inventory slots to the correct values*
* public void UpdateInventory()*
* {*
* Sprite[] toLoad = GameObject.Find(“Inventory”).GetComponent().inventory;*

* for (int i = 0; i < inventory.Length; i++)*
* {*
_ inventory*.sprite = toLoad[0];
}
}
}*_

If anyone knows why I’m getting this error please let me know.
Thanks in advance.

2

Have mercy this is extremely un-performant!

GameObject.Find("InventoryManager").GetComponent<InventoryManager>().UpdateInventory();
GameObject.Find("InventoryManager").GetComponent<InventoryManager>().UpdateHotbar();
GameObject.Find("InventoryManager").GetComponent<InventoryManager>().UpdateArmor();

I would strongly suggest reading my post :

Or at least cache the value before hand:

InventoryManager inventoryM;

void Awake()
{ inventoryM = GameObject.Find("InventoryManager").GetComponent<InventoryManager>(); }

void OtherVoid()
{
    inventoryM.UpdateInventory();
    inventoryM.UpdateHotbar();
    inventoryM.UpdateArmor();
}

But anytime you get a null reference it means the code cannot find the object you are looking for, to get the script component from. (As it always needs to get it from an object)

So I would study my method(the link I gave above) of doing things, and save yourself a ton of trouble… Not only now, but mainly later… Because nothing is worse than having to go back and re-do it all! ;)